Heat recovery unit and recirculation piping

While I may not be a plumber, I have been called a freon plumber. I do refrigeration and A/C and just got a deal on a heat recovery unit which uses the discharge line to heat water.

While I can easily figure out the A/C side of it, I am curious about the water side piping involving the tank. I also plan to add an active recirculation loop from the furthest fixture. And add pump @ tank.

Question is can someone tell me the correct way to pipe this configuration? Can't seem to find any diagrams on the internet and the HRU I got did not come with any directions. Have a 40gal tank with in, out, and drain port.

Also can anyone recommend a good grundfos recirc pump? House is on a well.

I'll have to get an exact model serial but it's a Trevor Martin. And yes it preheats the water. The hru says to tee off cold water supply at the tank and then pipe return into the drain. So I guess my next question is where do I pipe the return for the recirculation loop? Also in the drain?